Great visualization. However, there is another critically important part of what an API is/does. In addition to providing predictable outputs for inputs, an API insulates software applications from each other. As an example... if something were to go wrong with an application addresses to the Google Maps API and suddenly instead of presenting an address every second, 10,000 requests were made per second, without an API that throttles requests, the Google Maps API could crash and become unavailable to everyone trying to use it. Bad. Instead the API limits requests to what the internal program can handle, thereby making the input/output feature more reliable even when the programs providing the input become unreliable... or even hostile. Good. Without this ability to protect software, communication between web applications would be far more risky. APIs provide this critical protection and in so doing, make more functionality reliably available to everyone.
Great visualization. However, there is another critically important part of what an API is/does. In addition to providing predictable outputs for inputs, an API insulates software applications from each other. As an example... if something were to go wrong with an application addresses to the Google Maps API and suddenly instead of presenting an address every second, 10,000 requests were made per second, without an API that throttles requests, the Google Maps API could crash and become unavailable to everyone trying to use it. Bad. Instead the API limits requests to what the internal program can handle, thereby making the input/output feature more reliable even when the programs providing the input become unreliable... or even hostile. Good. Without this ability to protect software, communication between web applications would be far more risky. APIs provide this critical protection and in so doing, make more functionality reliably available to everyone.
One of the simplest explanation!